GTTS,
Give people some credit
as I understand it, the forwarder has joint legal responsibility for the package content, packaging, customs, value of goods and all other such stuff. The fact that the company exporting the goods, registered as dealing in chemicals, only shipping on an ad-hoc basis and on this occasion to Tehran, then yes, this should have been opened prior to getting air-side.
So, when were the loaders and pilots given this legal responsibility through IATA?